The present invention relates to apparatus for softening water; and more particularly to control valves for regenerating the resin bed of the water softening apparatus.
It is quite common for water drawn from a well to be considered “hard” in that it contains di-positive and sometimes tri-positive ions which have leached from mineral deposits in the earth. Such ions form insoluble salts with common detergents and soaps producing precipitates that increase the quantity of detergent or soap required for cleaning purposes. When hard water is used in boilers, evaporation results in the precipitation of insoluble residues that tend to accumulate as scale.
It is standard practice to install a water softener in the plumbing system of a building that is supplied with hard water. The most common kind of water softener is an ion exchange apparatus that has a tank which holds a bed of resin through which the hard water flows to remove undesirable minerals and other impurities. Binding sites in the resin bed initially contain positive ions, commonly unipositive sodium or potassium ions. As hard water enters the resin, competition for the binding sites occurs. The di-positive and tri-positive ions in the hard water are favored due to their higher charge densities and displace the unipositive ions. Two or three unipositive ions are displaced for each di-positive or tri-positive ion, respectively.
The capacity of the rein bed to absorb minerals and impurities is finite and eventually ceases to soften the water when a large percentage of the sites become occupied by the di-positive and tri-positive ions. When this occurs, it becomes necessary to recharge or regenerate the resin bed by flushing it with a regenerant, typically a solution of sodium chloride or potassium chloride. The concentration of unipositive ions in the regenerant is sufficiently high to offset the unfavorable electrostatic competition and the binding sites are recovered by unipositive ions.
Regeneration of early types of water softeners was affected manually only after it was discovered that the treatment capacity of the resin bed has been exceeded and the water flowing there through is no longer “soft.” In an effort to eliminate the need for manual regeneration, water softener control systems were provided with a mechanical clock which initiated water softener regeneration on a periodic basis. However, water usage typically varies so that regenerating a regular intervals may occur before it is actually required, thereby consuming more water and regenerate than is necessary, or regeneration may not occur soon enough resulting in hard water being fed throughout the building. As a result, demand type water softener controls have been developed which determine the remaining capacity of the resin bed to soften water. One type of such a demand type control system utilizes electrodes to measure the electrical conductivity of the resin bed and regeneration is initiated based on that measurement.
Regardless of the type of control system used to determine when to regenerate the resin bed, the control system activates a motor that operates a valve. The valve has several positions corresponding to the backwashing, brining, rinsing and brine replenishing steps of the regeneration process. The brining step draws the regenerant, typically a solution of a salt such as sodium chloride or potassium chloride, from a supply tank. At the end of the process, fresh water is set into the tank to produce a salt solution for the next regeneration procedure. It is important that the proper amount of salt solution be produced in the tank. To little solution will not effectively regenerate the resin bed, while to much will consume an excessive amount of salt during every regeneration cycle.
Heretofore, fresh water was added to the brine tank for a fixed period of time, as controlled by the speed of the motor which operated the water softener control valve. As a consequence, the actual amount of water that entered the brine tank varied depending upon the pressure of the water being supplied to the water softener. That pressure varies from installation to installation and from time to time at the same installation. Therefore, a given model of water softener replenished the salt solution to different amounts depending on the particular water pressure at that time.